Image Number 3 for United States Patent #7273555.
A process for continuous countercurrent ion exchange comprises piping a contaminated feed stream into a closed loop ion exchange contactor. The contactor is an ion exchange bed that has three or more reaction segments. The segments are comprised of at least an adsorption segment for treating the contaminated feed stream, a regeneration segment for stripping the contaminant ions from the resin bed, and a pulse segment for advancing the resin bed. Simultaneously, the feed stream is moved through the contactor in the same direction as the regeneration stream. Measuring the quality of this treated feed stream after it exits the contactor monitors the treatment capacity of the resin bed. In response to this quality measurement, the regenerated resin bed is advanced in the pulse segment of the contactor. The spent brine is recycled back to the contactor until the final effluent brine is highly concentrated. After the resin stops advancing, the feed stream and regeneration stream resume flow. Process water is recycled in four different steps of the ion exchange process, for the dilution of acid, as resin rinsing water, for back wash and during the resin pulsing stage.